One form of backing strip comprises a flat metal strip having a central longitudinal slot dividing the strip into a pair of rails and into which the neck portion of a molded rubber squeegee is positioned with the retention bead of the squeegee lying between the backing strip and the wiper superstructure. The rails may be joined at the ends of the strip if the slot is made to extend slightly less than the full length of the backing strip or the rails may be separate and coupled at the ends of the backing strip by means of a clip. In the former case, the squeegee itself has usually been fabricated with location means during a molding process whereas, in the latter, the squeegee may be fabricated by extrusion which greatly improves tolerances and consistency in the squeegee profile, thereby improving productivity and reducing costs.
Some backing strip structures comprising rail pairs have been proposed in which at least one rail is formed with a barb portion for penetrating the squeegee and to thereby prevent relative longitudinal movement between the backing strip and the squeegee and obviate the need to use a clip. Examples of such structures may be found in GB 2,243,991 and DE 3,208,749.
In both of these patents, the barb is longitudinally spaced from an abutment or notch-like structure which cooperates with a claw in the end yoke of a wiper superstructure to attach to the spine.
It will be understood that maximum stress is applied to the squeegee through the yokes of the superstructure where they are attached to each other, namely at the claws, and therefore that it is desirable to minimize said spacing between a barb and a notch.
It is also desirable to secure only one end of the squeegee so that the remainder of the squeegee can slide relative to the retaining structure and thereby adapt to the changing surface of a windshield, particularly in modern automobiles where the squeegee must wrap on a windshield having a pronounced curvature.
An object of this invention is to provide a method of fabricating such a spine structure which is economical and easy and to provide a structure for a backing strip which will reliably couple the squeegee to the windshield wiper superstructure by minimizing the longitudinal separation between squeegee retaining barbs and a claw retaining notch.